Supported Metal Carbido-cluster Catalysts PDF Download
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Author: Samir N. Salvi
Publisher:
ISBN:
Category :
Languages : en
Pages : 226
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Book Description
Author: Samir N. Salvi
Publisher:
ISBN:
Category :
Languages : en
Pages : 226
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
To understand the class of metal cluster catalysts better and to lay a foundation for the prediction of properties leading to improved catalysts, we have synthesized metal catalysts with well-defined structures and varied the cluster structures and compositions systematically--including the ligands bonded to the metals. These ligands include supports and bulky organics that are being tuned to control both the electron transfer to or from the metal and the accessibility of reactants to influence catalytic properties. We have developed novel syntheses to prepare these well-defined catalysts with atomic-scale control the environment by choice and placement of ligands and applied state-of-the art spectroscopic, microscopic, and computational methods to determine their structures, reactivities, and catalytic properties. The ligands range from nearly flat MgO surfaces to enveloping zeolites to bulky calixarenes to provide controlled coverages of the metal clusters, while also enforcing unprecedented degrees of coordinative unsaturation at the metal site--thereby facilitating bonding and catalysis events at exposed metal atoms. With this wide range of ligand properties and our arsenal of characterization tools, we worked to achieve a deep, fundamental understanding of how to synthesize robust supported and ligand-modified metal clusters with controlled catalytic properties, thereby bridging the gap between active site structure and function in unsupported and supported metal catalysts. We used methods of organometallic and inorganic chemistry combined with surface chemistry for the precise synthesis of metal clusters and nanoparticles, characterizing them at various stages of preparation and under various conditions (including catalytic reaction conditions) and determining their structures and reactivities and how their catalytic properties depend on their compositions and structures. Key characterization methods included IR, NMR, and EXAFS spectroscopies to identify ligands on the metals and their reactions; EXAFS spectroscopy and high-resolution STEM to determine cluster framework structures and changes resulting from reactant treatment and locations of metal atoms on support surfaces; X-ray diffraction crystallography to determine full structures of cluster-ligand combinations in the absence of a support, and TEM with tomographic methods to observe individual metal atoms and determine three-dimensional structures of catalysts. Electronic structure calculations were used to verify and interpret spectra and extend the understanding of reactivity beyond what is measurable experimentally.
Author: Paul J. Dyson
Publisher: CRC Press
ISBN: 1482283077
Category : Science
Languages : en
Pages : 180
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Book Description
Transition metal carbonyl clusters (TMCCs) continue to inspire great interest in chemical research, as much for their fascinating structures as for potential industrial applications conferred by their unique properties. This highly accessible book introduces the bonding, structure, spectroscopic properties, and characterization of clusters, and then explores their synthesis, reactivity, reaction mechanisms and use in organic synthesis and catalysis. Transition Metal Carbonyl Cluster Chemistry describes models and rules that correlate cluster structure with electron count, which are then applied in worked examples. Subsequent chapters explain how bonding relates to molecular structure, demonstrate the use of spectroscopic techniques such as NMR, IR and MS in cluster chemistry, and outline the factors contributing to the stability, dynamics and reactivity of clusters. The second part of this book discusses the synthesis and applications of TMCCs. It emphasizes the differences between the reactivities of clusters vs. mononuclear metal complexes, contingent to the availability of multiple-bonding sites and heterosite reactivity. The final chapters discuss reactions in which clusters act as homogeneous catalysts; including discussion on the use of solid and biphasic liquid-liquid supported clusters in heterogeneous catalysts. A useful reference for those commencing further research or post-graduate study on metal carbonyl clusters and advanced organometallic chemistry, this book is also a cornerstone addition to academic and libraries as well as private collections.
Author: Ailian Zhao
Publisher:
ISBN:
Category :
Languages : en
Pages : 436
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Author: Ghansham Panjabi
Publisher:
ISBN:
Category :
Languages : en
Pages : 606
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Author: R. T. K. Baker
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 258
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Author: Felix ShangChung Lai
Publisher:
ISBN:
Category :
Languages : en
Pages : 1092
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Author: Chia-Yu Fang
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Supported metal catalysts are essential for the petroleum industry, exemplified by alkane hydrocracking and reforming by Pt-containing zeolites. These catalysts, typically consisting of metal nanoparticles, are usually structurally complicated, impeding the fundamental understanding of catalytic processes. Molecular metal complexes/small metal clusters dispersed on the surface of oxide supports have drawn wide attention recently because they can be synthesized in a more structurally well-defined manner than traditional catalysts, leading the way toward the rational design for novel catalysis applications. When molecular-scale metal catalysts meet solid supports, the interaction of metal-support bonding is maximized. That is, supports are considered as giant ligands tuning the chemical properties of the metal centers, primarily explained by electronic effects. In this research, we report how less discussed confinement effects can play a role in (1) modification of catalytic properties of atomically dispersed metal catalysts and (2) selective syntheses of supported metal clusters with desired structures and sizes. Supported single-site Ir(I)(C2H4)2 complexes were prepared in multiple supports, including nearly nonporous materials, MgO and [gamma]-Al2O3, zeolites with large pore sizes, HY (13 Å) and HSSZ-53 (6.4 × 8.7 Å), and with medium pore sizes, H-Beta (5.5 × 7.0 Å). By using ethylene hydrogenation as the model reaction, the catalysis data show that Ir1 in the supports having much larger pore sizes than the molecular dimensions of ethylene, such as MgO, [gamma]-Al2O3, zeolite HSSZ-53 and zeolite HY, catalytic activity of Ir1 sites is majorly modified by electronic effects. In other words, Ir1 sites are more active when interacting with weaker electron-donating supports. However, Ir1 sites dispersed in zeolite H-Beta, having pore sizes comparable to the molecular dimensions of ethylene, perform superior activity although zeolite H-Beta has similar electron-donating strength to zeolite HY. This result was further bolstered by in-situ IR experiments, demonstrating that ethylene has the strongest interaction with Ir1 in zeolite H-Beta. We conclude that the confining environments of zeolite H-Beta stabilize the intermediate species in the catalytic cycle of ethylene hydrogenation and therefore enhance catalytic performance. Selective and precise synthesis of the prototype metal cluster, Rh4(CO)12, in the supercages of zeolite HY was achieved by using supported Rh(I)(CO)2 complexes as the precursor in the presence of CO and water vapor. Rh4(CO)12 is the metastable species and tends to be converted to thermodynamically stable Rh6(CO)16 via the traditional synthesis methods. Therefore, Rh4(CO)12 and Rh6(CO)16 typically present in a mixture, making selective syntheses of each of them challenging. In this work, confining environments of the supercages of zeolite HY were used to stabilize kinetically favored Rh4(CO)12. Selectivity of the Rh4(CO)12 synthesis was 100% with a high yield, >95%, characterized by infrared (IR) and X-ray absorption spectroscopy (XAS). Synthesized Rh4(CO)12 can be fully converted into Rh6(CO)16 by more forcing conditions, confirming that Rh4(CO)12 is the intermediate species of synthesizing Rh6(CO)16. The same approach was used to selectively prepare Ir4(CO)12 clusters in multiple molecular sieves, confirming that confining environments of solid supports can play a role in cluster syntheses. The cluster syntheses of Rh4−6 and Ir4 were observed to be reversible. The chemistry of cluster formation and fragmentation is coupled with the water gas shift-half reactions that add up to a complete water gas shift cycle.
Author: John Regalbuto
Publisher: CRC Press
ISBN: 1420006509
Category : Science
Languages : en
Pages : 490
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Book Description
This text explores the optimization of catalytic materials through traditional and novel methods of catalyst preparation, characterization, and monitoring for oxides, supported metals, zeolites, and heteropolyacids. It focuses on the synthesis of bulk materials and of heterogeneous materials, particularly at the nanoscale. The final chapters examine pretreatment, drying, finishing effects, and future applications involving catalyst preparation and the technological advances necessary for continued progress. Topics also include heat and mass transfer limitations, computation methods for predicting properties, and catalyst monitoring on laboratory and industrial scales.
Author: Philippe Serp
Publisher: John Wiley & Sons
ISBN: 3527830170
Category : Technology & Engineering
Languages : en
Pages : 912
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Book Description
b”Supported Metal Single Atom CatalysisCovers all key aspects of supported metal single atom catalysts, an invaluable resource for academic researchers and industry professionals alike Single atom catalysis is one of the most innovative and dynamic research areas in catalysis science. Supported metal catalysts are used extensively across the chemical industry, ranging from fine and bulk chemical production to petrochemicals. Single atom catalysts (SACs) combine the advantages of both homogeneous and heterogeneous catalysts such as catalyst stability, activity, and high dispersion of the active phase. Supported Metal Single Atom Catalysis provides an authoritative and up-to-date overview of the emerging field, covering the synthesis, preparation, characterization, modeling, and applications of SACs. This comprehensive volume introduces the basic principles of single atom catalysis, describes metal oxide and carbon support materials for SAC preparation, presents characterization techniques and theoretical calculations, and discusses SACs in areas including selective hydrogenation, oxidation reactions, activation of small molecules, C-C bond formation, and biomedical applications. Highlights the activity, selectivity, and stability advantages of supported metal SACs compared to other heterogeneous catalysts Covers applications of SACs in thermal catalysis, electrocatalysis, and photocatalysis Includes chapters on single atom alloys and supported double and triple metal atom catalysts Discusses the prospects, challenges, and potential industrial applications of SACs Supported Metal Single Atom Catalysis is an indispensable reference for all those working in the fields of catalysis, solid-state chemistry, materials science, and spectroscopy, including catalytic chemists, organic chemists, electrochemists, theoretical chemists, and industrial chemists.
